I managed to snag one of these at a local gunshow a couple of months ago. I have been after one of these ever since I shot one that belonged to Chaser3 at one of our Schutzenfests. This one was made for a South American contract but never left the country. It's got a great bore and the wood is near perfect. Still working up a decent loading for it.

Very nice find. TFB (The Firearm Blog) made a video talking about this rifle in the same caliber. There is something about the 7x57 caliber, easy to shoot but still gets the job done. Let us know how it shoots.

“We don’t rise to the level of our expectations – we fall to the level of our training” - Archilochus

Tommy many of these rifles were in the original 7x57mm Mauser. This was soon changed by the Mauser Bros to what we have today. There is a slight diff in case shape at the shoulder and neck area.
This is not a problem,they just look a little diff. To keep the brass usable make sure to anneal the brass after firing. Then neck size after that.
The action is very strong. They were not sure where smokeless powder was heading so the steel is over engineered.
I converted on rifle to .50-110-750 and have fired hundreds of .50 BMG bullets down range with no issues.
You'll love your new toy. They are fun to shoot.

Tin Can Sailor
'Nam Vet
NRA Endowment Member
President New Mexico Military Surplus Rifle Pistol Shooters

The 7x57mm Mauser cartridge was developed by Mauser for the Spanish 1893 rifle . The NO 5 rolling block was made starting in 1897 , and chambered in the Mauser cartridge , and sold as a secondary rifle to people using the 7x57mm Mauser rifle . Oversized military chambers, .288 + groove bores , but the same cartridge .